This invention relates to certain improvements in an automated pipetting system and, particularly, to an improved system with multiple pipetting probes which have individual positioning and individual metering controls.
Conventional automated pipetting systems are used to perform repetitive laboratory mixing, sampling or transferring of fluids in multiwell plates or multiple sets of vials or test tubes. Generally, one or more probes having fluid carrying tips are manipulated over an array of tubes by an arm which is robotically driven in three dimensions (X, Y, Z axes) to carry out programmed procedures under control of an associated computer. Desired procedures include dropping measured quantities of fluids into the tubes at specified depths, prewetting the probes' tips, blowing out the tips to clear them, touching the tips to samples or a cleaning surface and changing the tips.
However, conventional pipetting systems have a number of limitations. Many systems have only one probe with one tip. Some systems have changeable pipette heads with multiple tips in parallel, but all tips are controlled together so that each one dispense the same amount as the others. A few systems have independently metered probes, but they are not independently driven in the Z-axis (vertical) direction because the space taken up by the probe drive mechanisms would not fit the desired tight spacing of the plate wells of test tube array. Therefore, such systems can only drive all the probe tips together to the same depth in the wells or tubes. There are some systems with independent Z-axis drive for up to four probes, but the manner in which they are driven and supported preclude the possibility of automatically picking up and ejecting disposable tips or adding more probes. Because of the design of the supporting arm is typically only supported from the rear the precision to which the probes can be positioned in the Z-axis is compromised. None have an integral mixing table.